This invention relates to a method and apparatus for packing articles or goods with a composite stretched film and, more particularly, to a method and apparatus for packing goods stacked on a pallet by wrapping a composite film while mechanically elongating the same.
There are two types of stretchable films, one comprising an adhesive single layer film, and the other comprising a nonadhesive single layer film, and these two types are selectively used depending upon transportation conditions, shape and weight of the goods. The term "adhesive film" is used herein to mean a film made of adhesive thermoplastic resin such as an ethylenevinyl acetate copolymer, 1,2-polybutadiene and a styrenebutadiene copolymer. When applied with a slight pressure with a hand two superposed films readily bond together. The term "nonadhesive film" is used herein to mean a film made of a resin having no adhesive property, for example, crystallized polyolefine resins such as polyethylene, polypropylene and an ethylene-propylene copolymer.
Where these films are used for packing goods on a pallet, the adhesive film has the following advantages over the nonadhesive film.
1. When the film is wrapped a number of times, because films of respective layers bond with each other, an integral cylindrical body is obtained having improved breakage strength, tension strength and binding force. PA0 2. Since films bond together at overlapped portions, where a goods having an irregular surface are packed with the film, the film will be intimately positioned against surface of the goods thus forming a compact package. PA0 3. The end of the film can readily be secured to the goods by merely applying a small pressure with a hand without requiring a heat seal, tape application or use of a bonding agent. PA0 1. While being stored over a long time or during transportation (especially in the case of exported goods), the films of different goods bond together (blocking phenomenon) so that the films are broken when separating or unloading the goods. PA0 2. The blocking phenomenon makes difficult such handlings as piling up, and transfer of the goods with a fork lift or a crane. PA0 3. The adhesiveness imparting agent tends to precipitate on the surface of the film (bleeding phenomenon) thus contaminating the surface of the goods. PA0 4. Where the film is used to pack an assembly of light weight articles having smooth surfaces, for example glass bottles and aluminum cans, because the film directly bonds to the surfaces of the articles, at the time of removing the film, bottles or cans are bonded to the film resulting in the collapse of the assembly thus making it difficult to handle the articles. Thus, the adhesive film, now being used, has advantages and disadvantages pointed out hereinabove.
However, the adhesive film has the following disadvantages.